Project Summary Normal vision relies on the coordinated activity of numerous highly specialized cells organized within the eye and in projection areas within the brain. In the eye, the retina develops through a series of sequential cell differentiation steps tht culminate in the generation of the different retinal cell types properly organized within the laminated structure of the mature retina. A complex network of transcription factors and extracellular signaling molecules regulates this process. Although a number of the regulatory molecules that control fate specification and differentiation of retinal cells have been already identified, we are still far from a comprehensive understanding of the molecular mechanisms regulating retinal development. The long-term goal of this project is to identify key gene regulators of retinal progenitor cell differentiation in general and photoreceptor differentiation n particular. Within this framework, we have identified CTCF, a multifunctional transcriptional regulator previously unknown to participate in these phenomena, as a leading candidate in regulating several aspects of retinal cell differentiation. Based on our observations we have hypothesized that CTCF regulates the initial specification of neural retina progenitor cells from the pool of uncommitted progenitors within the optic vesicle, and promotes their subsequent survival and differentiation toward a photoreceptor lineage. We will use loss- and gain-of-function approaches, and their complementary phenoytype-rescue strategies, to investigate these hypotheses. These studies will contribute to a better understanding of the mechanisms driving retina development in normal and diseased conditions and to build up an integrated network of the molecules involved in this process. This knowledge in turn, is expected to have a significant impact on the potential prevention of developmental abnormalities of the retina and the development of feasible stem cell-based therapeutic treatments for retinal degenerative diseases.